Electric hoist



F. H. WITTBERGER 2,710,738

ELECTRIC HOIST 2 Sheets-Sheet 1 June 14, 1955 Filed March 2, 1953INVENTOR. Zno'JL/K W Q 2 MIT hm NIT June 1955 F. H. WlTTB ERGER ELECTRICHOIST 2 Sheets-Sheet 2 Filed March 2, 1955 ELECTRIC HOIST Frank H.Wittberger, West Allis, Wis, assignor to llarnischfeger Corporation,Milwaukee, Wis, a corporation of Wisconsin Application March 2, 1953,Serial No. 339,557

7 Claims. (Cl. 254186) This invention relates to electric hoists forwinding in and paying out a line or cable and it more specificallyresides in a hoist having a cable winding drum and a motor joined with ashaft extending into the drum to drive a gear reduction train housedwithin the drum, the drum being mounted for rotation upon spacedbearings carried in a frame having a part which extends through one ofthe bearings and provides means for resisting the reaction of the gearreduction train, the gear reduction train sometimes comprising anepicyclic planetary unit of high driving ratio with irreversibleproperties so that a mechanical load brake may be dispensed with, themotor being sometimes provided with means causing its rotor to moveaxially to release a motor brake.

It is desirable that an electric hoist. be compact, simple and rugged.To this end it is important that the space within the winding drum beutilized, to house parts which would otherwise add to the dimensions ofthe apparatus. It is also desirable that the rather large ratio ofdriving reduction which is required be accomplished with as few parts aspossible. It is furthermore desirable that means be included which willreliably prevent an unintended descent of the load or descent of theload at a rate more rapid than intended and to do so without resort toso-called friction load brakes which are subject to alteration inadjustment due to wear and temperature changes.

It is an object of this invention to provide a hoist for winding in andpaying out a cable or line of rugged construction requiring lessmaintenance.

It is another object of this invention to provide a hoist with a gearreduction drive for the winding drum housed within the drum to permit acompact arrangement having minimum overall dimensions.

It is another object of this invention to provide a gear reduction drivefor a hoist that affords the advantages of the foregoing objects inwhich only two sets of gear teeth are in mesh and in which anexceptionally large number of teeth of each set are engaged so that Wearis minimized.

It is another object of this invention to provide a hoist with a windingdrum in which a drive motor is mounted on one side and a brake ismounted on the opposite side and in which an axial thrust delivered bythe motor is transmitted through the drum to the brake to release thesame.

It is still another object of this invention to provide a hoist in whichunintended descent of a load or a descent at a rate faster than thatdesired is prevented by an irreversible reduction gear train in which alarge number of gear teeth are continuously in engagement to provide anexceptionally high factor of safety.

These and other objects and advantages of this invention will appear inthe description to follow. In the description reference is made to theaccompanying drawings in which there is shown by way of illustration andnot of limitation one specific form in which this invention may beembodied.

In the drawings:

Fig. 1 is a side view in elevation and in section of an electric hoistin which this invention is embodied,

* atent Patented June 14, 1955 Fig. 2 is a view in cross section of thehoist shown in Fig. I viewed through the plane 2-2, and

Fig. 3 is a view in cross section of the hoist shown in Fig. 1 Viewedthrough the plane 33.

Referring now to the drawings, more particularly Fig. 1, numeral 1designates a main hoist frame comprising a centrally disposed drumhanger 2, generally cylindrical, and open beneath to permit a cable toextend downwardly from Within the hanger 2. A bracket 3 integral withthe upper portion of the drum hanger Z rises upwardly and provides meansfor attachment to an overhead support. Bolted to the left hand side ofthe drum hanger 2, as a part of the main frame 1, is a motor bracket 4that forms a support for a motor frame 5 of an electric motor 6. Themotor bracket 4 includes a bell housing 7 that extends inwardly to sealone end of the motor 6 and to support a drum mounting hub 8 having acentral opening.

Bolted to the right hand side of the drum hanger 2, as a part of themain frame 1, is a brake bracket 9 having a shroud plate It? extendinginwardly and terminating in a second hub 11 in the form of a truncatedcone open at the center. Non-rotatably secured within the hub 11 bymeans of a key is the shank 13 of an internal reaction gear 12. Gear 12acts as an orbit gear for an epicyclic planetary system to be described.

A bearing 14 fitted within the hub 8 of the motor bracket 4, and abearing 15 seated upon the shank 13 of the gear 12, provide meansmounting a cable winding drum lo for rotation. The drum in is formed intwo parts comprising the winding drum 1! having a hub at its right handend supported by the ball bearing. 15 and an internal drum gear 18 keyedto the inner face of the drum l7 having a hub 19 supported within thebearing 14;. The internal drum gear 18 has a slightly larger pitchdiameter than gear 12 and like the reaction gear 12 forms a part of aplanetary system to be described.

The frame 5 of the motor 6 has a bell housing 20 at the outer end inwhich is mounted a roller bearing 21 held in place by a retaining ring22. A motor drive shaft 23 with a bushing 24 carried on its left handend is supported by and is free to rotate and to move axially within theroller bearing 21. The shaft 23 after a reduction in diameter extends tothe right from the frame 5 and passes through the cable winding drum 16.From the drum 16 the shaft 23 continues through the hub 11 and thereaction gear 12 to the right hand side of the shroud plate ill.

The larger left hand end of shaft 23 serves as a mounting for a motorrotor 25 secured thereto. The construction of rotor 25 differs from thatusually employed in that a series of circumferential slots 26 are cut inits outer periphery. The stator 27 of the motor 6 also includes a seriesof circumferentially disposed slots 28 that extend across the polefaces. As shown in Fig. 1, the rotor 25 is disposed in a standstillposition which occurs when the motor 6 is not energized and in thisstandstill position the slots 26 are slightly to the left of and out ofalignment with the stator slots 28. Upon energization of the stator 27the magnetic attraction between the stator 27 and rotor 25 urges therotor 25 axially to the right toward a position of alignment between theslots 26 and the slots 28. The motor 6 thus, while exerting torque, alsoexerts an axial thrust upon energization of the field 27 that isimparted to the drive shaft 23.

Splined to the central portion of the shaft 23 is an eccentric quill 29.The left hand end of quill 29 abuts a set of shims 30 that bear in turnupon a bushing 31, disposed in contact with the shoulder 32 formed bythe increased diameter of the shaft 23. The eccentric quill 29 issupported in a pair of roller bearings 34 and 33, mounted respectivelyin the drum gear 18 and the reaction gear 12. The output shaft 23 isthus supported by the roller bearings 21, 33 and 34 each of which isconstructed to permit axial shift of the shaft 23 together with theeccentric quill 29.

Mounted for rotation upon the quill 29, eccentrically disposed withrespect to the shaft 23, is a compound planetary pinion 35, carried onroller bearings 36. The pinion 35 is cut with two distinct planetpinions 38 and 39 of slightly different pitch diameters, coordinatedwith the diameters of gears 12 and 18 so that planet pinion 38 isdisposed in mesh with the reaction gear 12 which is fixed with respectto the frame 1, and planet pinion 39 is disposed in mesh with the drumgear 18. Mounted on either side of and retaining the planetary pinion 35in position is a pair of counterweights 40 and 41 secured by pins 37 tothe eccentric quill 29. The counterweights 40 and 41 are positioned tocounterbalance rotational forces of the parts that gyrate about theshaft 23 which would otherwise be dynamically unbalanced. Placing theweights 40, 41 on both sides of the pinion 35 also reduces unwantedradial thrusts imparted to the supporting bearings.

The throw of eccentric 29 is approximately one-half the difference inthe pitch diameters of pinion 38 and gear 12 on the one hand or one halfthe difference in pitch diameters of pinion 39 and gear 18. Uponrotation of the eccentric member 29 drum 16 will advance or retreat,depending upon the direction of rotation of member 29, an angulardistance dependent upon the reduction ratio of the epicyclic gear train.This reduction ratio is approximately equal to the product of the ratiosof the number of teeth in gear 38 divided by the difference in number ofteeth between gears 12 and 38 and the number of teeth in gear 18 dividedby the difference in number of teeth between gears 18 and 39. In atypical case gear 12 may have fifty-eight teeth, pinion 38, fifty-twoteeth, gear 18, sixty-four teeth and pinion 39, fifty-eight teeth. Inthis case the ratios are 52:6 and 64:6 and the product of these ratiosgives a reduction of approximately 92.4 to l.

The epicyclic gear train thus provided, has a very large driving ratioof reduction, comprises but two gears and one compound pinion, and asappears in Figs. 2 and 3, a large number of teeth are at all times incontact. The transmission is moreover self-locking since its efiiciencyis determined largely by tooth friction and the efiiciency quotient isless than the reverse driving ratio.

Carried upon the right hand end of the shaft 23 with a splinedconnection is an elongated collar 42 which abuts the right hand end ofthe eccentric quill 29 to act as a continuation thereof for thetransmission of axial thrust exerted by the motor 6. The collar 42 isformed to provide a toothed spider 43 that engages the toothed centralopening in a brake disc 44 to cause the latter to turn with shaft 23.Axial forces exerted by the motor 6 are not however transmitted throughthe coupling between the spider 43 and disc 44. Brake elementsassociated with the disc 44 for frictional engagement therewith comprisethe shroud plate 10 and a movable brake plate 45 to the right of thedisc 44. Plate 45 is free to move axially but is restrained fromrotation by pin 46 seated in the shroud plate 10. Brake plate 45 is openat its center and is threaded to receive a tubular collar 47 that isslidingly mounted on a stationary boss 48 at its right hand end. Thecollar 47 has an internal shoulder 49 disposed toward its left hand endthat bears against a thrust bearing 50 mounted upon the end of the motorshaft 23 and abutting the collar 42. A brake spring 51 encircles thecollar 47 to urge the brake plate 45 against the brake disc 44 which inturn is urged against the shroud plate 10. The internal shoulder 49 ofthe collar 47 is urged against the thrust bearing 50 by reason of theaction of the brake spring 51 thus acting to move the shaft 23 when themotor 6 is not energized axially to the left of its running position. Ahousing plate 52 that supports the boss 48 and acts as a stationaryreaction for the spring 51 closes the end of the brake bracket 9 toenclose the brake members.

The opposite side of the plate 52 may serve as a mounting for electricalswitches and controlling apparatus for the hoist which may be enclosedby a cover 53.

The lower side of the brake bracket 9 is open at 54 to admit av pendantcontrol cord not shown but intended to be attached to a switch leverdesignated by reference numeral 55. To secure the hoist cable to thedrum 16 the dead end is fitted with an end fitting received within thecable socket 56.

To adjust for the desired length of the axial stroke of the shaft 23 thecollar 47 which is threaded to the brake plate 45 is turned to aposition that forms a gap between the collar 47 and the housing plate 52that is equivalent to the stroke desired. This adjustment is made withthe braking elements in braking position tightly sandwiching the brakedisc 44 between the shroud 16 and the piate 45. The shims 30 between thebushing 31 and left hand end of the eccentric quill 29 are employed toprovide an adjustment for the axial offset between the slots 26 in thearmature 25 and the slots 28 in the field member 27. It has been founddesirable to adjust the collar 47 and employ such thickness of shims 3%to ensure an axial stroke of about onethird the offset between the slots26 and 28. When so adjusted upon energization of the motor 6 the axialthrust at ing from the attractive force acting to move the at; are 25toward alignment of the slots 26 with the slots will be adequate torelease the brake.

Release of the brake members 10, 44 and 45 is immediately followed byrotation of the drive shaft 23 which acts to rotate the cable drum 16through the planetary gear train within the drum 16. The motor 6 may bedriven to either pay out or wind in hoisting cable.

Because of the high ratio of reduction in the eccentric planetary andthe inherent friction of such a driving system the gearing isirreversible and the load will not travel faster in either raising orlowering directions than the inherent limiting speed of the motor 6. Thegear is also self locking and the need for a load brake is thereforeeliminated.

I claim:

1. In an electric hoist the combination comprising a frame providingspaced bearing supports; a hollow cable winding drum mounted on spacedbearings supported by said spaced bearing supports; a motor mounted onsaid frame on one side of said drum having an axially displaceable rotorwith an output shaft extending through each of said hearings to the sideof said drum opposite said motor; said rotor and shaft having a runningposition assumed upon energization of said motor and a standstillposition axially displaced from said running position; torque increasingreduction gearing housed Within said hollow drum having input means indriven relation to said motor output shaft, output means in drivingrelation to said drum, and reaction means sustaining the increasedtorque thereof; means secured to said frame and extending through one ofsaid bearings secured to said reaction means to maintain the samestationary; a brake disposed to the side of said drum opposite that ofsaid thrust motor cooperatively engaged with said output shaft andhaving a pair of axially separable brake members movable to disengagedposition upon movement of said rotor and shaft to said running position;and bias means urging said brake members into engagement to retard shaftrotation and urging said rotor and shaft axially to said standstillposition when said motor is deenergized, brake releasing thrust beingdelivered by said motor upon energization thereof through said shaft todisengage said brake members and to move said rotor and shaft to runningposition.

2. In an electric hoist the combination comprising a mounting frameproviding spaced bearing supports; a hollow cable winding drum rotatablymounted on spaced bearings supported by said bearing supports; a motormounted on said frame on one side of said drum having an output shaftextending through said bearings emerging from the side of said drumopposite said motor; a brake disposed to the side of said drum oppositesaid motor cooperatively engaged with said shaft for release uponenergization of said motor, an eccentric member mounted on said shaftwithin said drum, a pinion gear mounted on said eccentric member androtatable with respect thereto having two sets of teeth to form a pairof planets, a ring gear forming an extension of said frame extendingthrough one of said bearings for said drum to within said drum disposedin mesh with one of said planets, and a second ring gear fixed to aninterior wall of said drum in mesh with the second of said planets torotatably drive said drum in response to motion of said pinion gear.

3. In an electric hoist the combination comprising a central drumassembly including a rotatable hollow cable receiving drum having acentrally disposed bearing support at one end, a reaction gear memberwith a central opening having a shank extending through and borne by abearing in said bearing support and a reaction end within said drum, aquill with one end extending within the central opening of said reactiongear member rotationally supported thereby, reduction gearing withinsaid drum with a gear member in mesh with said reaction gear member andhaving an input supported by said quill and an output, a drum gearsecured within said drum for rotation therewith in driven relation tothe output of said reduction gearing and having a centrally disposed hubat the end of said drum opposite said bearing support, and a bearinghoused within said hub supporting the end of said quill opposite the endreceived in said reaction gear member; a motor disposed at one side ofsaid drum assembly having a frame member supporting said motor andsupporting the hub of said drum gear for rotation, said motor having anaxially displaceable output shaft with an axially displaceable armaturemounted thereon, said shaft having an end extending through and slidablewith respect to said quill for rotation thereof; a brake housingdisposed at the side of said drum assembly opposite said motor having abrake frame member rigidly secured to the shank of said reaction gearmember and the frame of said motor; and brake elements within said brakehousing operable between brake engaged and brake released positions inrc sponse to axial movement of said motor output shaft.

4. In an electric hoist the combination comprising a rotatable hollowcable receiving drum having a centrally disposed bearing support at oneend; a reaction member with a central opening having a shank extendingthrough and borne by a bearing in said bearing support and a reactionend within said drum; a quill having an eccentric and with one endextending within the central opening of said reaction memberrotationally supported thereby; a drum gear member fitted within the endof said drum opposite said bearing support for rotation with said drumand having a centrally disposed hub; a bearing housed within said hubsupporting the end of said quill opposite the end received in saidreaction gear member; reduction gearing within said drum having a pinionmounted on the eccentric of said quill free to rotate with respectthereto and to be gyrated in response to rotation thereof having twosets of teeth to form a pair of planets, a fixed ring gear forming apart of said reaction member in mesh with one of said planets, and asecond ring gear in mesh with the other of said planets supported bysaid drum gear member; a motor disposed at one side of said drum havinga frame member supporting said motor and supporting the hub of said drumgear for rotation, said motor having an axially displaceable outputshaft with an axially displaceable armature mounted thereon, said shafthaving an end extending through and slidable with respect to said quillfor rotation thereof and extending through the central opening in saidreaction member; a brake housing disposed at the side of said drumopposite said motor having a brake frame member rigidly secured to theshank of said reaction member and the frame of said motor; and brakeelements within said brake housing operable between brake engaged andbrake released positions in response to axial movement of said motoroutput shaft.

5. An electric hoist in accordance with claim 4 having counterweightsattached to said quill at both sides of said pinion to counterbalancerotational forces of said pinion and eccentric member.

6. In an electric hoist the combination comprising a rotatable hollowcable receiving drum having a centrally disposed bearing support at oneend, a reaction gear member with a central opening having a shankextending through and borne by a bearing in said bearing support and areaction end within said drum, a drum gear fitted within the end of saiddrum opposite said bearing support for rotation therewith and having acentrally disposed hub, a motor disposed at one side of said drum havinga frame member supporting said motor and supporting the hub of said drumgear for rotation, said motor having an axially displaceable outputshaft with an axially displaceable armature mounted thereon and havingan end extending through said drum and extending within the centralopening of said reaction gear member, said output shaft being rotatablyborne by a bearing in said hub of said drum gear and a bearing in theshank of said reaction gear member, reduction gearing within said drumhaving agear member in mesh with said reaction gear member with an inputdriven by said output shaft and an output in driving relation to saiddrum gear, a brake housing disposed at the side of said drum opposites'aid'motor having a brake frame member rigidly secured to the shank ofsaid reaction gear member and the frame of said motor, and brakeelements within said brake housing operable between brake engaged andbrake released positions in response to axial movement of said outputshaft.

7. An electric hoist in accordance with claim 6 in which said reductiongearing includes an eccentric Within said drum mounted on and rotatablewith said output shaft, a pinion mounted upon said eccentric free torotate with respect thereto and to be gyrated in response to rotation ofsaid output shaft having two sets of teeth to form a pair of planets,one of said planets being in mesh with a fixed ring gear forming a partof said reaction gear member, and the other of said planets being inmesh with a ring gear forming a part of said drum gear.

References Cited in the file of this patent UNITED STATES PATENTS1,384,839 Krohn July 19, 1921 1,771,281 Wilsing July 22, 1930 2,239,839Benson Apr. 29, 1941 2,354,387 Lawler July 25, 1944

